Fully evolved magnetohydrodynamic (MHD) turbulence in an infinite medium has the statistical property of scale invariance which is an exact form of self-similarity, that is, its statistical properties are unchanged as we move from scale to scale subject to a rescaling. As a consequence of this, bulk quantities of MHD turbulent flows exhibit scaling laws within the inertial range seen as power law power scaling in the power spectrum and as multiscaling for the various moments of the structure function. Either when turbulence is not completely evolved (low Reynolds numbers) or the system is bounded, then symmetries in the flow are broken and the similarity is lost. Nevertheless, a generalized similarity or extended self-similarity is recovered, which implies a generalized scaling for the structure functions. The generalized similarity has been observed in several turbulent plasmas (e.g. in the polar solar wind and in a quiescent prominence) and it points to a universal feature of finite range MHD turbulence. The aim of this project is to test whether this generalized similarity is in fact universal by analysing different turbulent plasmas in finite sized systems.
Centre for Fusion, Space and Astrophysics
Department of Physics
University of Warwick
Coventry, CV4 7A, UK